The present invention relates to a balancing arrangement more particularly to a balancing arrangement of a hollow rotating member, such as a drive shaft for a motor vehicle.
Balancing arrangements by the use of counterweights are known as such in the prior art. Various arrangements have been proposed which rely on fastening counterweights in the position or positions as determined on balancing machines rotating the part to be balanced. These machines are known as such, for example, in connection with balancing the wheels of automobiles where counterweights are attached in predetermined positions on the rim of the wheel.
With the advent of drive shafts for motor vehicles made from light-weight metal such as aluminum or aluminum alloy which have to be balanced, the pre-existing method of balancing such drive shafts consisted of welding counterweights of predetermined size and weight in predetermined positions. This type of drive shaft, contrary to prior art drive shafts, is of hollow aluminum construction and larger diametric dimension than the prior art solid drive shafts. Because the aluminum drive shafts have a wall thickness of about 2.2 mm., the counterweights must be welded to the outer surface of the corresponding cylindrical end piece of the universal joint which is made of a wall thickness of about 5 mm. However, the welding operation not only requires a longer cylindrical end piece of the universal joint to accommodate the largest counterweights and their welded connections, as will be explained more fully hereinafter, but additionally is both time-consuming and costly and always entails also problems inherent with welded connections.
It is therefore a principal object of the present invention to provide a balancing arrangement which avoids the aforementioned shortcomings and drawbacks encountered with the prior art balancing arrangements and which is both simple and relatively inexpensive in installation and at the same time assures a permanent positioning of the counterweight without the need for welding operations.
The underlying problems are solved according to the present invention in that a counterweight of predetermined size and weight is affixed to the external surface of the rotating member by the use of a clamping band made from a material such as stainless steel devoid of any significant elastic stretchability in the longitudinal direction to which elastic stretchability in the longitudinal direction is imparted by a special configuration of the clamping band involving openings located preferably opposite the area where the open clamping band is interconnected over the counterweight. This entails additional advantages as will also be explained more fully hereinafter. If the open ends of the clamping band are interconnected by a separate connecting member provided with a so-called xe2x80x9cOetikerxe2x80x9d ear, then the connecting member can advantageously be used as part of the counterweight whose significance is enhanced by the oppositely disposed openings in the band. The clamping band in accordance with the present invention permits a simple and relatively rapid installation of the counterweight while at the same time assuring that the counterweight is held in its predetermined position.
According to another feature of the present invention, the counterweight may be provided with anchoring means in its internal surfaces so that under the tightening forces applied by the clamping band, it will anchor itself securely in the external surface of the rotating member. These anchoring means may be obtained by ragged non-deburred edges realized, for example, by the use of a dull stamping tool when cutting out the counterweight. In the alternative, the internal surfaces of the counterweights may be roughened by any known subsequent surface treatment or may offer such rough internal surfaces by the use of an appropriate selection of material composition in its manufacture.
The clamping band may also be provided with anchoring means to preclude lateral movement along the external surfaces of the rotating member. The anchoring means in the clamping band can most appropriately be obtained again by ragged non-deburred edges produced by the use of relatively dull stamping tools, particularly when stamping out the sections with openings that impart elastic stretchability to the clamping band.
According to still another feature of the present invention, each counterweight may be provided with outwardly protruding, cold-deformed hook-like members which are spaced from each other by a distance approximately corresponding to the width of the clamping band and defining therebetween a channel receiving the clamping band so that any relative lateral movements between the clamping band and the counterweight are essentially prevented.
According to a still further feature of the present invention, the counterweights are not flat but may be curved with a radius of curvature at least slightly smaller than the radius of curvature of the external surfaces of the rotating member and are made from a material thickness that will adapt itself elastically to the external surfaces of the rotating member under the forces applied to the counterweight by the clamping band.